text: # Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
  # Spack Project Developers. See the top-level COPYRIGHT file for details.
  #
  # SPDX-License-Identifier: (Apache-2.0 OR MIT)
  
  import os
  import stat
  import sys
  import errno
  import hashlib
  import tempfile
  import getpass
  from six import string_types
  from six import iteritems
  
  import llnl.util.tty as tty
  from llnl.util.filesystem import mkdirp, can_access, install, install_tree
  from llnl.util.filesystem import partition_path, remove_linked_tree
  
  import spack.paths
  import spack.caches
  import spack.cmd
  import spack.config
  import spack.error
  import spack.mirror
  import spack.util.lock
  import spack.fetch_strategy as fs
  import spack.util.pattern as pattern
  import spack.util.path as sup
  import spack.util.url as url_util
  
  from spack.util.crypto import prefix_bits, bit_length
  
  
  # The well-known stage source subdirectory name.
  _source_path_subdir = 'spack-src'
  
  # The temporary stage name prefix.
  stage_prefix = 'spack-stage-'
  
  
  def _create_stage_root(path):
      """Create the stage root directory and ensure appropriate access perms."""
      assert path.startswith(os.path.sep) and len(path.strip()) > 1
  
      err_msg = 'Cannot create stage root {0}: Access to {1} is denied'
  
      user_uid = os.getuid()
  
      # Obtain lists of ancestor and descendant paths of the $user node, if any.
      group_paths, user_node, user_paths = partition_path(path,
                                                          getpass.getuser())
  
      for p in group_paths:
          if not os.path.exists(p):
              # Ensure access controls of subdirs created above `$user` inherit
              # from the parent and share the group.
              par_stat = os.stat(os.path.dirname(p))
              mkdirp(p, group=par_stat.st_gid, mode=par_stat.st_mode)
  
              p_stat = os.stat(p)
              if par_stat.st_gid != p_stat.st_gid:
                  tty.warn("Expected {0} to have group {1}, but it is {2}"
                           .format(p, par_stat.st_gid, p_stat.st_gid))
  
              if par_stat.st_mode & p_stat.st_mode != par_stat.st_mode:
                  tty.warn("Expected {0} to support mode {1}, but it is {2}"
                           .format(p, par_stat.st_mode, p_stat.st_mode))
  
              if not can_access(p):
                  raise OSError(errno.EACCES, err_msg.format(path, p))
  
      # Add the path ending with the $user node to the user paths to ensure paths
      # from $user (on down) meet the ownership and permission requirements.
      if user_node:
          user_paths.insert(0, user_node)
  
      for p in user_paths:
          # Ensure access controls of subdirs from `$user` on down are
          # restricted to the user.
          if not os.path.exists(p):
              mkdirp(p, mode=stat.S_IRWXU)
  
              p_stat = os.stat(p)
              if p_stat.st_mode & stat.S_IRWXU != stat.S_IRWXU:
                  tty.error("Expected {0} to support mode {1}, but it is {2}"
                            .format(p, stat.S_IRWXU, p_stat.st_mode))
  
                  raise OSError(errno.EACCES, err_msg.format(path, p))
          else:
              p_stat = os.stat(p)
  
          if user_uid != p_stat.st_uid:
              tty.warn("Expected user {0} to own {1}, but it is owned by {2}"
                       .format(user_uid, p, p_stat.st_uid))
  
  
  def _first_accessible_path(paths):
      """Find the first path that is accessible, creating it if necessary."""
      for path in paths:
          try:
              # Ensure the user has access, creating the directory if necessary.
              if os.path.exists(path):
                  if can_access(path):
                      return path
              else:
                  # Now create the stage root with the proper group/perms.
                  _create_stage_root(path)
                  return path
  
          except OSError as e:
              tty.debug('OSError while checking stage path %s: %s' % (
                        path, str(e)))
  
      return None
  
  
  def _resolve_paths(candidates):
      """
      Resolve candidate paths and make user-related adjustments.
  
      Adjustments involve removing extra $user from $tempdir if $tempdir includes
      $user and appending $user if it is not present in the path.
      """
      temp_path = sup.canonicalize_path('$tempdir')
      user = getpass.getuser()
      tmp_has_usr = user in temp_path.split(os.path.sep)
  
      paths = []
      for path in candidates:
          # Remove the extra `$user` node from a `$tempdir/$user` entry for
          # hosts that automatically append `$user` to `$tempdir`.
          if path.startswith(os.path.join('$tempdir', '$user')) and tmp_has_usr:
              path = path.replace("/$user", "", 1)
  
          # Ensure the path is unique per user.
          can_path = sup.canonicalize_path(path)
          if user not in can_path:
              can_path = os.path.join(can_path, user)
  
          paths.append(can_path)
  
      return paths
  
  
  # Cached stage path root
  _stage_root = None
  
  
  def get_stage_root():
      global _stage_root
  
      if _stage_root is None:
          candidates = spack.config.get('config:build_stage')
          if isinstance(candidates, string_types):
              candidates = [candidates]
  
          resolved_candidates = _resolve_paths(candidates)
          path = _first_accessible_path(resolved_candidates)
          if not path:
              raise StageError("No accessible stage paths in:",
                               ' '.join(resolved_candidates))
  
          _stage_root = path
  
      return _stage_root
  
  
  def _mirror_roots():
      mirrors = spack.config.get('mirrors')
      return [
          sup.substitute_path_variables(root) if root.endswith(os.sep)
          else sup.substitute_path_variables(root) + os.sep
          for root in mirrors.values()]
  
  
  class Stage(object):
      """Manages a temporary stage directory for building.
  
      A Stage object is a context manager that handles a directory where
      some source code is downloaded and built before being installed.
      It handles fetching the source code, either as an archive to be
      expanded or by checking it out of a repository.  A stage's
      lifecycle looks like this::
  
          with Stage() as stage:      # Context manager creates and destroys the
                                      # stage directory
              stage.fetch()           # Fetch a source archive into the stage.
              stage.expand_archive()  # Expand the archive into source_path.
              <install>               # Build and install the archive.
                                      # (handled by user of Stage)
  
      When used as a context manager, the stage is automatically
      destroyed if no exception is raised by the context. If an
      excpetion is raised, the stage is left in the filesystem and NOT
      destroyed, for potential reuse later.
  
      You can also use the stage's create/destroy functions manually,
      like this::
  
          stage = Stage()
          try:
              stage.create()          # Explicitly create the stage directory.
              stage.fetch()           # Fetch a source archive into the stage.
              stage.expand_archive()  # Expand the archive into source_path.
              <install>               # Build and install the archive.
                                      # (handled by user of Stage)
          finally:
              stage.destroy()         # Explicitly destroy the stage directory.
  
      There are two kinds of stages: named and unnamed.  Named stages
      can persist between runs of spack, e.g. if you fetched a tarball
      but didn't finish building it, you won't have to fetch it again.
  
      Unnamed stages are created using standard mkdtemp mechanisms or
      similar, and are intended to persist for only one run of spack.
      """
  
      """Shared dict of all stage locks."""
      stage_locks = {}
  
      """Most staging is managed by Spack.  DIYStage is one exception."""
      managed_by_spack = True
  
      def __init__(
              self, url_or_fetch_strategy,
              name=None, mirror_paths=None, keep=False, path=None, lock=True,
              search_fn=None):
          """Create a stage object.
             Parameters:
               url_or_fetch_strategy
                   URL of the archive to be downloaded into this stage, OR
                   a valid FetchStrategy.
  
               name
                   If a name is provided, then this stage is a named stage
                   and will persist between runs (or if you construct another
                   stage object later).  If name is not provided, then this
                   stage will be given a unique name automatically.
  
               mirror_paths
                   If provided, Stage will search Spack's mirrors for
                   this archive at each of the provided relative mirror paths
                   before using the default fetch strategy.
  
               keep
                   By default, when used as a context manager, the Stage
                   is deleted on exit when no exceptions are raised.
                   Pass True to keep the stage intact even if no
                   exceptions are raised.
  
              path
                   If provided, the stage path to use for associated builds.
  
              lock
                   True if the stage directory file lock is to be used, False
                   otherwise.
  
              search_fn
                   The search function that provides the fetch strategy
                   instance.
          """
          # TODO: fetch/stage coupling needs to be reworked -- the logic
          # TODO: here is convoluted and not modular enough.
          if isinstance(url_or_fetch_strategy, string_types):
              self.fetcher = fs.from_url_scheme(url_or_fetch_strategy)
          elif isinstance(url_or_fetch_strategy, fs.FetchStrategy):
              self.fetcher = url_or_fetch_strategy
          else:
              raise ValueError(
                  "Can't construct Stage without url or fetch strategy")
          self.fetcher.set_stage(self)
          # self.fetcher can change with mirrors.
          self.default_fetcher = self.fetcher
          self.search_fn = search_fn
          # used for mirrored archives of repositories.
          self.skip_checksum_for_mirror = True
  
          self.srcdir = None
  
          # TODO: This uses a protected member of tempfile, but seemed the only
          # TODO: way to get a temporary name.  It won't be the same as the
          # TODO: temporary stage area in _stage_root.
          self.name = name
          if name is None:
              self.name = stage_prefix + next(tempfile._get_candidate_names())
          self.mirror_paths = mirror_paths
  
          # Use the provided path or construct an optionally named stage path.
          if path is not None:
              self.path = path
          else:
              self.path = os.path.join(get_stage_root(), self.name)
  
          # Flag to decide whether to delete the stage folder on exit or not
          self.keep = keep
  
          # File lock for the stage directory.  We use one file for all
          # stage locks. See spack.database.Database.prefix_lock for
          # details on this approach.
          self._lock = None
          if lock:
              if self.name not in Stage.stage_locks:
                  sha1 = hashlib.sha1(self.name.encode('utf-8')).digest()
                  lock_id = prefix_bits(sha1, bit_length(sys.maxsize))
                  stage_lock_path = os.path.join(get_stage_root(), '.lock')
  
                  Stage.stage_locks[self.name] = spack.util.lock.Lock(
                      stage_lock_path, lock_id, 1)
  
              self._lock = Stage.stage_locks[self.name]
  
          # When stages are reused, we need to know whether to re-create
          # it.  This marks whether it has been created/destroyed.
          self.created = False
  
      def __enter__(self):
          """
          Entering a stage context will create the stage directory
  
          Returns:
              self
          """
          if self._lock is not None:
              self._lock.acquire_write(timeout=60)
          self.create()
          return self
  
      def __exit__(self, exc_type, exc_val, exc_tb):
          """
          Exiting from a stage context will delete the stage directory unless:
          - it was explicitly requested not to do so
          - an exception has been raised
  
          Args:
              exc_type: exception type
              exc_val: exception value
              exc_tb: exception traceback
  
          Returns:
              Boolean
          """
          # Delete when there are no exceptions, unless asked to keep.
          if exc_type is None and not self.keep:
              self.destroy()
  
          if self._lock is not None:
              self._lock.release_write()
  
      @property
      def expected_archive_files(self):
          """Possible archive file paths."""
          paths = []
  
          fnames = []
          expanded = True
          if isinstance(self.default_fetcher, fs.URLFetchStrategy):
              expanded = self.default_fetcher.expand_archive
              fnames.append(os.path.basename(self.default_fetcher.url))
  
          if self.mirror_paths:
              fnames.extend(os.path.basename(x) for x in self.mirror_paths)
  
          paths.extend(os.path.join(self.path, f) for f in fnames)
          if not expanded:
              # If the download file is not compressed, the "archive" is a
              # single file placed in Stage.source_path
              paths.extend(os.path.join(self.source_path, f) for f in fnames)
  
          return paths
  
      @property
      def save_filename(self):
          possible_filenames = self.expected_archive_files
          if possible_filenames:
              # This prefers using the URL associated with the default fetcher if
              # available, so that the fetched resource name matches the remote
              # name
              return possible_filenames[0]
  
      @property
      def archive_file(self):
          """Path to the source archive within this stage directory."""
          for path in self.expected_archive_files:
              if os.path.exists(path):
                  return path
          else:
              return None
  
      @property
      def expanded(self):
          """Returns True if source path expanded; else False."""
          return os.path.exists(self.source_path)
  
      @property
      def source_path(self):
          """Returns the well-known source directory path."""
          return os.path.join(self.path, _source_path_subdir)
  
      def fetch(self, mirror_only=False):
          """Downloads an archive or checks out code from a repository."""
          fetchers = []
          if not mirror_only:
              fetchers.append(self.default_fetcher)
  
          # TODO: move mirror logic out of here and clean it up!
          # TODO: Or @alalazo may have some ideas about how to use a
          # TODO: CompositeFetchStrategy here.
          self.skip_checksum_for_mirror = True
          if self.mirror_paths:
              # Join URLs of mirror roots with mirror paths. Because
              # urljoin() will strip everything past the final '/' in
              # the root, so we add a '/' if it is not present.
              urls = []
              for mirror in spack.mirror.MirrorCollection().values():
                  for rel_path in self.mirror_paths:
                      urls.append(url_util.join(mirror.fetch_url, rel_path))
  
              # If this archive is normally fetched from a tarball URL,
              # then use the same digest.  `spack mirror` ensures that
              # the checksum will be the same.
              digest = None
              expand = True
              extension = None
              if isinstance(self.default_fetcher, fs.URLFetchStrategy):
                  digest = self.default_fetcher.digest
                  expand = self.default_fetcher.expand_archive
                  extension = self.default_fetcher.extension
  
              # Have to skip the checksum for things archived from
              # repositories.  How can this be made safer?
              self.skip_checksum_for_mirror = not bool(digest)
  
              # Add URL strategies for all the mirrors with the digest
              for url in urls:
                  fetchers.insert(
                      0, fs.from_url_scheme(
                          url, digest, expand=expand, extension=extension))
  
              if self.default_fetcher.cachable:
                  for rel_path in reversed(list(self.mirror_paths)):
                      cache_fetcher = spack.caches.fetch_cache.fetcher(
                          rel_path, digest, expand=expand,
                          extension=extension)
                      fetchers.insert(0, cache_fetcher)
  
          def generate_fetchers():
              for fetcher in fetchers:
                  yield fetcher
              # The search function may be expensive, so wait until now to
              # call it so the user can stop if a prior fetcher succeeded
              if self.search_fn and not mirror_only:
                  dynamic_fetchers = self.search_fn()
                  for fetcher in dynamic_fetchers:
                      yield fetcher
  
          for fetcher in generate_fetchers():
              try:
                  fetcher.set_stage(self)
                  self.fetcher = fetcher
                  self.fetcher.fetch()
                  break
              except spack.fetch_strategy.NoCacheError:
                  # Don't bother reporting when something is not cached.
                  continue
              except spack.error.SpackError as e:
                  tty.msg("Fetching from %s failed." % fetcher)
                  tty.debug(e)
                  continue
          else:
              err_msg = "All fetchers failed for %s" % self.name
              self.fetcher = self.default_fetcher
              raise fs.FetchError(err_msg, None)
  
      def check(self):
          """Check the downloaded archive against a checksum digest.
             No-op if this stage checks code out of a repository."""
          if self.fetcher is not self.default_fetcher and \
             self.skip_checksum_for_mirror:
              tty.warn("Fetching from mirror without a checksum!",
                       "This package is normally checked out from a version "
                       "control system, but it has been archived on a spack "
                       "mirror.  This means we cannot know a checksum for the "
                       "tarball in advance. Be sure that your connection to "
                       "this mirror is secure!")
          elif spack.config.get('config:checksum'):
              self.fetcher.check()
  
      def cache_local(self):
          spack.caches.fetch_cache.store(
              self.fetcher, self.mirror_paths.storage_path)
  
      def cache_mirror(self, stats):
          """Perform a fetch if the resource is not already cached"""
          dst_root = spack.caches.mirror_cache.root
          absolute_storage_path = os.path.join(
              dst_root, self.mirror_paths.storage_path)
  
          if os.path.exists(absolute_storage_path):
              stats.already_existed(absolute_storage_path)
              return
  
          self.fetch()
          spack.caches.mirror_cache.store(
              self.fetcher, self.mirror_paths.storage_path,
              self.mirror_paths.cosmetic_path)
          stats.added(absolute_storage_path)
  
      def expand_archive(self):
          """Changes to the stage directory and attempt to expand the downloaded
          archive.  Fail if the stage is not set up or if the archive is not yet
          downloaded."""
          if not self.expanded:
              self.fetcher.expand()
              tty.msg("Created stage in %s" % self.path)
          else:
              tty.msg("Already staged %s in %s" % (self.name, self.path))
  
      def restage(self):
          """Removes the expanded archive path if it exists, then re-expands
             the archive.
          """
          self.fetcher.reset()
  
      def create(self):
          """
          Ensures the top-level (config:build_stage) directory exists.
          """
          # Emulate file permissions for tempfile.mkdtemp.
          if not os.path.exists(self.path):
              mkdirp(self.path, mode=stat.S_IRWXU)
          elif not os.path.isdir(self.path):
              os.remove(self.path)
              mkdirp(self.path, mode=stat.S_IRWXU)
  
          # Make sure we can actually do something with the stage we made.
          ensure_access(self.path)
          self.created = True
  
      def destroy(self):
          """Removes this stage directory."""
          remove_linked_tree(self.path)
  
          # Make sure we don't end up in a removed directory
          try:
              os.getcwd()
          except OSError as e:
              tty.debug(e)
              os.chdir(os.path.dirname(self.path))
  
          # mark as destroyed
          self.created = False
  
  
  class ResourceStage(Stage):
  
      def __init__(self, url_or_fetch_strategy, root, resource, **kwargs):
          super(ResourceStage, self).__init__(url_or_fetch_strategy, **kwargs)
          self.root_stage = root
          self.resource = resource
  
      def restage(self):
          super(ResourceStage, self).restage()
          self._add_to_root_stage()
  
      def expand_archive(self):
          super(ResourceStage, self).expand_archive()
          self._add_to_root_stage()
  
      def _add_to_root_stage(self):
          """
          Move the extracted resource to the root stage (according to placement).
          """
          root_stage = self.root_stage
          resource = self.resource
  
          if resource.placement:
              placement = resource.placement
          elif self.srcdir:
              placement = self.srcdir
          else:
              placement = self.source_path
  
          if not isinstance(placement, dict):
              placement = {'': placement}
  
          target_path = os.path.join(
              root_stage.source_path, resource.destination)
  
          try:
              os.makedirs(target_path)
          except OSError as err:
              tty.debug(err)
              if err.errno == errno.EEXIST and os.path.isdir(target_path):
                  pass
              else:
                  raise
  
          for key, value in iteritems(placement):
              destination_path = os.path.join(target_path, value)
              source_path = os.path.join(self.source_path, key)
  
              if not os.path.exists(destination_path):
                  tty.info('Moving resource stage\n\tsource : '
                           '{stage}\n\tdestination : {destination}'.format(
                               stage=source_path, destination=destination_path
                           ))
  
                  src = os.path.realpath(source_path)
  
                  if os.path.isdir(src):
                      install_tree(src, destination_path)
                  else:
                      install(src, destination_path)
  
  
  @pattern.composite(method_list=[
      'fetch', 'create', 'created', 'check', 'expand_archive', 'restage',
      'destroy', 'cache_local', 'cache_mirror', 'managed_by_spack'])
  class StageComposite:
      """Composite for Stage type objects. The first item in this composite is
      considered to be the root package, and operations that return a value are
      forwarded to it."""
      #
      # __enter__ and __exit__ delegate to all stages in the composite.
      #
  
      def __enter__(self):
          for item in self:
              item.__enter__()
          return self
  
      def __exit__(self, exc_type, exc_val, exc_tb):
          for item in reversed(self):
              item.keep = getattr(self, 'keep', False)
              item.__exit__(exc_type, exc_val, exc_tb)
  
      #
      # Below functions act only on the *first* stage in the composite.
      #
      @property
      def source_path(self):
          return self[0].source_path
  
      @property
      def expanded(self):
          return self[0].expanded
  
      @property
      def path(self):
          return self[0].path
  
      @property
      def archive_file(self):
          return self[0].archive_file
  
  
  class DIYStage(object):
      """
      Simple class that allows any directory to be a spack stage.  Consequently,
      it does not expect or require that the source path adhere to the standard
      directory naming convention.
      """
  
      """DIY staging is, by definition, not managed by Spack."""
      managed_by_spack = False
  
      def __init__(self, path):
          if path is None:
              raise ValueError("Cannot construct DIYStage without a path.")
          elif not os.path.isdir(path):
              raise StagePathError("The stage path directory does not exist:",
                                   path)
  
          self.archive_file = None
          self.path = path
          self.source_path = path
          self.created = True
  
      # DIY stages do nothing as context managers.
      def __enter__(self):
          pass
  
      def __exit__(self, exc_type, exc_val, exc_tb):
          pass
  
      def fetch(self, *args, **kwargs):
          tty.msg("No need to fetch for DIY.")
  
      def check(self):
          tty.msg("No checksum needed for DIY.")
  
      def expand_archive(self):
          tty.msg("Using source directory: %s" % self.source_path)
  
      @property
      def expanded(self):
          """Returns True since the source_path must exist."""
          return True
  
      def restage(self):
          raise RestageError("Cannot restage a DIY stage.")
  
      def create(self):
          self.created = True
  
      def destroy(self):
          # No need to destroy DIY stage.
          pass
  
      def cache_local(self):
          tty.msg("Sources for DIY stages are not cached")
  
  
  def ensure_access(file):
      """Ensure we can access a directory and die with an error if we can't."""
      if not can_access(file):
          tty.die("Insufficient permissions for %s" % file)
  
  
  def purge():
      """Remove all build directories in the top-level stage path."""
      root = get_stage_root()
      if os.path.isdir(root):
          for stage_dir in os.listdir(root):
              if stage_dir.startswith(stage_prefix) or stage_dir == '.lock':
                  stage_path = os.path.join(root, stage_dir)
                  remove_linked_tree(stage_path)
  
  
  def get_checksums_for_versions(
          url_dict, name, first_stage_function=None, keep_stage=False):
      """Fetches and checksums archives from URLs.
  
      This function is called by both ``spack checksum`` and ``spack
      create``.  The ``first_stage_function`` argument allows the caller to
      inspect the first downloaded archive, e.g., to determine the build
      system.
  
      Args:
          url_dict (dict): A dictionary of the form: version -> URL
          name (str): The name of the package
          first_stage_function (callable): function that takes a Stage and a URL;
              this is run on the stage of the first URL downloaded
          keep_stage (bool): whether to keep staging area when command completes
  
      Returns:
          (str): A multi-line string containing versions and corresponding hashes
  
      """
      sorted_versions = sorted(url_dict.keys(), reverse=True)
  
      # Find length of longest string in the list for padding
      max_len = max(len(str(v)) for v in sorted_versions)
      num_ver = len(sorted_versions)
  
      tty.msg("Found {0} version{1} of {2}:".format(
              num_ver, '' if num_ver == 1 else 's', name),
              "",
              *spack.cmd.elide_list(
                  ["{0:{1}}  {2}".format(str(v), max_len, url_dict[v])
                   for v in sorted_versions]))
      tty.msg('')
  
      archives_to_fetch = tty.get_number(
          "How many would you like to checksum?", default=1, abort='q')
  
      if not archives_to_fetch:
          tty.die("Aborted.")
  
      versions = sorted_versions[:archives_to_fetch]
      urls = [url_dict[v] for v in versions]
  
      tty.msg("Downloading...")
      version_hashes = []
      i = 0
      for url, version in zip(urls, versions):
          try:
              with Stage(url, keep=keep_stage) as stage:
                  # Fetch the archive
                  stage.fetch()
                  if i == 0 and first_stage_function:
                      # Only run first_stage_function the first time,
                      # no need to run it every time
                      first_stage_function(stage, url)
  
                  # Checksum the archive and add it to the list
                  version_hashes.append((version, spack.util.crypto.checksum(
                      hashlib.sha256, stage.archive_file)))
                  i += 1
          except FailedDownloadError:
              tty.msg("Failed to fetch {0}".format(url))
          except Exception as e:
              tty.msg("Something failed on {0}, skipping.".format(url),
                      "  ({0})".format(e))
  
      if not version_hashes:
          tty.die("Could not fetch any versions for {0}".format(name))
  
      # Find length of longest string in the list for padding
      max_len = max(len(str(v)) for v, h in version_hashes)
  
      # Generate the version directives to put in a package.py
      version_lines = "\n".join([
          "    version('{0}', {1}sha256='{2}')".format(
              v, ' ' * (max_len - len(str(v))), h) for v, h in version_hashes
      ])
  
      num_hash = len(version_hashes)
      tty.msg("Checksummed {0} version{1} of {2}".format(
          num_hash, '' if num_hash == 1 else 's', name))
  
      return version_lines
  
  
  class StageError(spack.error.SpackError):
      """"Superclass for all errors encountered during staging."""
  
  
  class StagePathError(StageError):
      """"Error encountered with stage path."""
  
  
  class RestageError(StageError):
      """"Error encountered during restaging."""
  
  
  class VersionFetchError(StageError):
      """Raised when we can't determine a URL to fetch a package."""
  
  
  # Keep this in namespace for convenience
  FailedDownloadError = fs.FailedDownloadError
  